Module 1.1: Introduction (cont.)

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Module 1.1 Introduction (cont.)

• Business Goals and Constraints
• Analyzing Technical Goals

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Understanding the Customer

• A good network design must recognize the
  customers requirements - need to make sure your
  design meets THEIR needs and not just YOURS!
• The Customer may be your own firm, the who
  you are designing the network for
• Need an overview of a customers requirements

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Business Goals

• Before we look at the technical details, we first
  start at the business goals
• Start with researching your clients business
• what industry are they in
• their market
• their suppliers
• their products
• their services
• the competition they face

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Business Goals - Continued

• Need to understand the organizational structure
  of the client
• their separate departments
• lines of business
• vendors
• partners
• remote offices
• This will help characterize traffic flow and
  determine user communities

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Business Goals - Continued

• When you understand the corporate structure, you
  also identify who the key decision makers are,
  who will have final say on your design proposal
  when you are finished
• You want to understand what are the overall goal
  of the network design project

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Questions to Ask

• Why are they doing the network design analysis?
• What will the network be used for?
• How does the customer think the new network will
  improve their business practices?
• What is the criteria to be used to judge the
  network?

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Success Criteria

• What makes the network design a success?
• May be defined differently by the different
  stakeholders
• company executives
• managers
• end users
• network administrators
• system programmers
• any other person or group who has a stake in the
  network design project

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Failure Consequences

• What happens if the project does not meet the
  design objectives?
• How visible is the project to upper management?
• To what extent could unforeseen behavior of the
  new network disrupt business operations?

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The Internet Impact

• The growth of the Internet has made
  interconnection with it almost a business
  priority for network design
• Vast amounts of information is now being shared
  within the organization using the internet as a
  design example, normally called Intranets.

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Typical Business Goals

• Increase revenue and profit
• Improve corporate communications
• Shorten product development cycles
• Build partnerships with other companies
• Expand into other markets
• Modernize out-dated technologies
• Reduce network costs
• Make more data available to more people
• Improve network security and reliability

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Business Constraints

• Politics and Policies
• Are there people who would like to see you fail?
• What are the companies policy on suppliers
• Budget and Staffing Constraints
• Your design must fit the budget
• Staff abilities may determine some of your design
• Scheduling

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Analyzing Technical Goals
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Analyzing Technical Goals

• Now that we have discussed Business Goals, lets
  examine the Technical Goals that we need to
  understand and should reflect in the design of a
  network
• You need to match your network design to fit the
  customers technical needs

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Technical Goals Constraints

• Scalability
• Availability
• Network Performance
• Utilization, Throughput, Accuracy, Efficiency,
  Delay, and Response Time
• Security
• Manageability
• Usability
• Adaptability
• Affordability

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Scalability

• Scalability - how much growth a network design
  must support
• Need to examine the network needs out a few years
  - 3 years as a minimum
• Key points to understand
• How many more sites will be added?
• How extensive will the networks be at each site?
• How many more users will be added?
• How many more servers will be added?

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Availability

• Availability is the amount of time a network is
  available to users
• Can be expressed as percent uptime
• 165 hours in 168 hours/week 98.21
• Redundancy is used to increase a networks
  availability
• Availability is also tied to disaster recovery
• 99.70 - 30 minutes outage every week

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Network Performance

• There are several measures to look at
• Utilization
• Throughput
• Accuracy
• Efficiency A key measure
• Protocol Frame Size, Protocol Overhead, and
  Routing Protocol Overhead
• Delay
• Response Time

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Network Performance - Utilization

• Is the percent of total available capacity
  (bandwidth) in use
• Bandwidth is measured over a time interval to
  determine the amount in use
• There are several numbers used to describe when
  your network shows delays that impact the
  usability of the network - will will examine
  these later.

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Network Performance - Throughput

• Throughput is defined as the quantity of
  error-free data successfully transferred between
  nodes per unit of time
• Depends on network access method, the load on the
  network and the error rate
• Throughput can be expressed in Packets per Second
  (PPS) than can be sent by a device with dropping
  any packets

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Network Performance -Accuracy

• Accuracy is a measure to ensure that the data
  received at the destination must be the same as
  the data sent by the source
• Data errors are caused by power surges, or
  spikes, poor physical connections, failing
  devices and electrical noise
• Accuracy can be expressed in Bit Error Rate
  (BER), typically 1 in 105

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Network Performance -Efficiency

• We measure how effective an operation is
• How much overhead is needed to send traffic
  across the network - the traffic has our data in
  it
• Overhead is due to several factors lets look at
  some of them
• Network Protocol Frame Size
• Network Protocol Overhead
• Routing Protocol Overheads

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Efficiency and Network Protocol Frame Sizes

• Since application data is sent over frames and
  each frame can hold some data. Key is how many
  frames do I need to sent my data? (each frame has
  some overhead in it)
• Novell IPX 1,500 byte Frame Size
• Telnet is only 60 bytes
• HTTP (Web) is 1,500 bytes
• Token Ring uses 4,096 bytes
• ATM used 53 byte cells

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Efficiency and Network Protocol Frame Sizes
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Efficiency and Network Protocol Overhead

• Remember data is packaged in protocol frames that
  contain overhead data, some have more overhead
  than others
• Ethernet - 38 bytes per frame
• IP - 20 bytes per frame
• TCP - 20 bytes per frame
• IPX - 30 bytes per frame
• ATM - 5 bytes per cell

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Efficiency and Network Protocol Overhead
802.2 Logical Link Control header used with
Ethernet and Token Ring
Ethernet w LLC
Token Ring w LLC
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Efficiency and Routing Protocol Overheads

• Remember each routing protocol also use up
  network bandwidth
• IP RIP - every 30 seconds sends 532 byte packages
• IP IGRP - every 90 seconds sends 1,488 byte
  packages
• IPX SAP - every 60 seconds sends a 480 byte
  package

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Efficiency and Routing Protocol Overheads
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Network Performance -Efficiency - Summary

• You want to use a protocol that has a large frame
  size, and one that also needs only small header
  information in each frame
• You want an efficient Routing Protocol
• This allows us to transfer more data at a higher
  efficiency across our network!

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Network Performance - Delay

• Interactive applications demand minimal delay
  when receiving a data stream
• Delay must be constant for voice and video
  applications other wise you will get jitter
  causing disruptions in voice quality and
  jumpiness in video streams
• Delay can be caused by physics, and by network
  devices that move the data within a network (use
  buffers to minimize effect)

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Network Performance - Queuing Delay

• Queuing delay is the number of packets in a queue
  on a packet switching device
• As utilization increases, more packets must wait
  in the queue before being put on the wire
• Queue depth utilization/(1-utilization)

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Network Performance - Response Time

• Response time is a network performance goal that
  users care about most
• Users recognize the amount of time to receive a
  response from the network system
• Users begin to get frustrated when response time
  is 100ms (.1 seconds) or so

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Security

• Security design is getting to be one of the most
  important aspects of network design
• Network design must ensure against loss of
  business data or disruption of business activity
• Need to understand the risk of data loss
• Need to understand ways to get to the data
• Need to understand who wants the data

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Manageability

• There are different ways to manage a network and
  the different things to manage
• Performance management
• Fault management
• Configuration management
• Security management
• Accounting management

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Usability

• Usability refers to the ease-of-use with which
  network users can access the network and services
• Focus is on making the network users job easier
• example is using host naming servers and easy to
  use configuration devices such as a DHCP server

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Adaptability

• You want to ensure the network can implement new
  technologies in the future
• You want it to be able to adapt and change with
  technology
• A flexible network can also adapt to changing
  network patterns and quality of service (QoS)
  requirements

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Affordability

• Affordability is sometimes called
  cost-effectiveness
• Want to carry the maximum amount of traffic for a
  given financial cost
• Financial costs include non-recurring equipment
  costs and recurring network operating costs
• WAN costs are an area where a good design can
  save